This application claims the priority benefit of European Patent Application No. 01107649.4, filed on Mar. 28, 2001, and entitled xe2x80x9cAbsolute Trackwidth Measurement on Magnetic Recording Heads.xe2x80x9d
1. Field of the Invention
The present invention relates in general to magnetic recording heads. More specifically it relates to the measurement of the track width of such heads.
2. Background of the Invention
In a magnetic disk drive, data is written and read by magnetic transducers called xe2x80x9cheadsxe2x80x9d which are positioned over a disk while it is rotated at a high speed. Magnetic heads are mounted on sliders that are supported over a surface of the disk by a thin cushion of air (an xe2x80x9cair bearingxe2x80x9d) produced by the disk""s high rotational speed. In order to increase the amount of data stored per unit of disk surface area (xe2x80x9careal densityxe2x80x9d), more data must be written in narrower tracks on the disk surface.
Read/write heads are manufactured by a costly and complicated process. First, the read/write elements are applied to a wafer. This is normally done by thin film technology, thereby applying very thin layers by sputtering and electroplating. These layers are subsequently given their coherent shape by etching techniques. The wafer thus treated is then sawed up in order to be treated further mechanically.
One principal means of improving areal density of magnetic recording is to improve the number of data tracks which a write head can record on a disk; the related parametric expression is xe2x80x9ctracks per inchxe2x80x9d or xe2x80x9cTPIxe2x80x9d. The TPI capability of a write head is increased by decreasing the head dimension which determines the width of a data track; typically this dimension is called the head xe2x80x9ctrack widthxe2x80x9d.
The above mentioned wafer process is traditionally controlled with optical width, which defines the junction between the sensor and the hard bias/leads material. However, this junction is not defined sharply.
The track width of the read head is determined by the width of the GMR (Giant Magneto Resistive) sensor material at the air bearing surface (ABS). Since the dimensions of magnetic heads are decreasing rapidly, the track width now enters regions at the wavelength of light, i.e.,  less than 500 nm. Thus, useful optical measurements will become extremely difficult and SEM measurements are complicated to carry out since there is no material contrast between the active sensor area and the adjacent lead structure. This is due to the fact that both the sensor and the lead area may be provided with tantalum layers as protective caps during manufacture of the heads.
FIG. 1 shows the definition of the magnetic read width (marked by the two arrows) which has been measured using a SEM with high sensitivity/low current. The K5-Final is measured using traditional optical microscopes, whereby a measurement sensitivity below 600 nm only allows degraded tracking of process variations. In addition, process control based on photo measurement assumes stable milling and deposition processes.
When using SEM methods, what is measured is not the track width directly, but the photo resist being present above the structure before the etching process.
In addition, using high current SEM in order to penetrate the tantalum protective layer, will destroy the respective material.
Thus, a need exists for a method to adequately directly measure the absolute track width on narrow track magnetic recording heads.
It is therefore an object of the present invention to provide a method that allows measuring the absolute track widths being in the area of the wavelength of light.
It is a further object of the invention to provide such a method that allows a respective measurement without destroying the respective material.
These and other objects and advantages are achieved by the method disclosed in the claims.
Advantageous embodiments of the invention are described in the dependent claims.